Basically, PBL has 3 processes toward the study.
1. Identify facts.
When you go to the interview session, they will pass out a sheet with a story/description on it. Then, you have to identify what is fact and what is not important.
2. Making Ideas
Based on the facts the group lists, you guys start to make ideas. It is not necessary right idea, but you want to have your reasoning to support your idea BASED on the fact.
3. Learning Needs
Since there are many ideas the group comes out (some are right, but some are not), you want to decide the group learning needs to study the topics.
Then, the interviewer will pass out another sheet with more detail information comparing to the first sheet you guys just discuss. Follow the above processes again.
During the interview, you want to speak, discuss, and help each other. They are not looking for the super intelligent person, but the person who can cooperate with people. That is the spirit of PBL - Student Based Learning.
During the lunch, talk to your group members and come out the way you guys can demonstrate the NON-COMPETITIVE way to help each other.